Neutron Brillouin Scattering by using pulsed spallation source - spin dynamics from Berry phase ferromagnet -

Yasuo Endoh (Institute for Materials Structure, KEK & Tohoku University, Japan)

Neutron Brillouin Scattering (NBS) method was applied at the high resolution chopper spectrometer (HRC) installed at JPARC. This method itself is rather classic but it has been developed recently by using higher energy pulsed neutrons by which we can extend to measure 10 meV excitations in forward direction (down to less than 1 degree of scattering angle). We aimed to study spin dynamics from powder samples since the large single crystals are not always available for neutron inelastic scattering method. Then we developed the high energy resolution as well as low neutron background specifically in low angle scattering direction. By using NBS method we have recently studied spin dynamics in SrRuO_3 of Berry Phase ferromagnet where the large spin wave gap appears in the cubic lattice (not exactly cubic) and emerges the unusual thermal evolution. We anticipate this unconventional result suggest the existence of the magnetic monopole or at least the robust spin orbit coupling in this material.

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